Problem: Simplify the following expression: $x = \dfrac{9}{4n} \div \dfrac{5}{9n}$
Solution: Dividing by an expression is the same as multiplying by its inverse. $x = \dfrac{9}{4n} \times \dfrac{9n}{5}$ When multiplying fractions, we multiply the numerators and the denominators. $x = \dfrac{ 9 \times 9n } { 4n \times 5}$ $x = \dfrac{81n}{20n}$ Simplify: $x = \dfrac{81}{20}$